532 High End RPM Problem

[asra]

Hello everyone,After completing my first Gyro fitted with a Rotax 532 which i had to buy a new exhaust system for ,it has no power from 5000-6000 rpm ,narrowed the problem down to the exhaust system by opening one of the flange joints slightly to relieve back pressure.I know this is not recommended on any 2 stroke but I got sick to death of changing jets.The vendor of the exhaust said to send the muffler back and they would replace it but after doing a few measurements i think it might be the 90 degree bend shortening the expansion chamber.It only measures 5" from 1 end to the side ,the specs say it should be 6 and 5 eights. Is there any body that can measure there 532/582 90 degree system and let me know the correct lenght of the 90 degree elbow connected to the y pipe. Any help would be very much appreciated. Peter Adams

[asra]

Peter, is it a genuine Rotax part?. If it is your problem is elseware. What are your EGT's at full power?.Are the carbies put together properly,ie needle and clip in the right position?.The distance "Weld to weld" on the 90* joint is 5 inches.

[asra]

Thanks Murray,the carbs are new,new points,egts both read 950 with standard jets and i have tried different jets with no joy .I even dropped the pitch of the prop 1 degree from reccomended.The only thing that makes any difference is relieving backpressure.The engine runs and starts very well.It will run to 6000rpm but it is very slow in pickup and uncontrolable between 5000-6000rpm .The engine runs very well with the joint open as shown in the photo below.Image Insert: 81.37

[asra]

Peter, I hope you don't mind but I have made the pic a bit easier to see.Aussie Paul.[]Image Insert: 43.62

[asra]

Thanks Paul,Any suggestions and dont say put a subaru on it![]

[Tim]

Peter, have you got a photo of the outlet end of the muffler and has the muffler been modified in any way? If the mixture is too rich it can cause this problem, especially with a long heavy prop. What is the prop and what is the length and pitch? Your EGT readings suggest too rich (unless they are in C, then it would be too lean).Tim McClure

[asra]

With egts @ 950 I'd say to rich, because motor bikes will run very lean when exhaust comes lose or off & this would explain extra revs with exhaust openBut if you'v been playing with carbys then could be dead plugs have you changed them Butch

[Echo]

Peter, what fuel & fuel/oil mixture are you using ? Does it make any difference if you run without aircleaners ?

[asra]

Question, if you run a fuel oil mix of 50 to 1 and then change to 40 to 1 will the engine run leaner, richer or the same?Aussie Paul. []www.firebirdgyros.com

[asra]

Tim, The prop is a 3 blade 64" brolga with 13degree pitch blocks it was 14 degrees. Just spent all afternoon cutting my new exhaust to pieces ,What a job,and opened up a few baffle ports with the drill.My egt's now showing a bit over a 1000degrees and I have full control between 5000-6000 but 6000 is the max it will rev to, so yes now the muffler has been modified[] and my chance of exchanging it at Bert Flood is no longer an option.I run 50:1 premium unleaded mix and although the egt's are only showing a bit over a 1000 the plugs look a bit on the lean side,so yes Paul I might still try a 40:1 mix just for interest sake.

[asra]

Tim, that seems like too much pitch to me for that diameter prop. I guess it depends on what pitch the tips are at. What do you reckon?Aussie Paul.[]www.firebirdgyros.com

[Greg Mitchell]

G'Day Peter,Did you buy Rod Martin's gyro and change out the 503 for the 532?Hope you get your engine sorted. Sure is a nice gyro that one of Rod's.Cheers,Mitch.www.thebutterflyllc.com

[asra]

950 degrees EGT is way to low. You are loading the engine down to much with that amount of pitch. Ideal full throttle readings are 1200*,although I would accept lower than that when static as engine RPM and EGT's will increase in the air.Aim for about 6500 RPM in a full throttle climb.

[asra]

Hi Mitch,built my machine from scratch,I think a guy in Vic. bought Rod's gyro.Thanks Murray,Forgot that I might pick up a few revs from static to flying have to get off my but and get it registared and test flown.

[Greg Mitchell]

G'Day Pete,Mate touched base with Jamo last night, he bought me up to speed on your progress and gyro. Congrats and Safe Flying as you approach Solo. Hope to catchup early in the new year. Cheers Pete.Mitch.www.thebutterflyllc.com